Add and document custom properties

Editor assessment

fix(toast) says custom properties are added and documented, with a reference footer for the issue. The toast scope fits, and the type straddles fix and docs, which the guidance treats as a taxonomy rather than a communication flaw. The subject is imperative and unterminated. No body lists the properties or explains the motivation, so detail is thin, but the intent is clear. Understandable and publishable with a modest context gap.